#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "compiler.h"
#include "symtab.h"


static void write_func_params(struct pair_tn *params, struct node *list) {
	if (list->type == N_LIST_END) return;
	assert(list->child1->type == N_VAR_DECL);
	params[0].type = list->child1->rtype;
	params[0].name = strdup(list->child1->name);
	write_func_params(params + 1, list->child2);
}

static void write_node_list(struct node **dest, struct node *list) {
	if (list->type == N_LIST_END) return;
	dest[0] = list->child1;
	write_node_list(dest + 1, list->child2);
}

static bool oper_is_basic_arith(enum operator oper) {
	return oper == OP_ADD || oper == OP_SUB || oper == OP_MUL || oper == OP_DIV || oper == OP_MOD;
}

static bool oper_is_comparison(enum operator oper) {
	return oper == OP_EQ || oper == OP_NEQ ||
	       oper == OP_LT || oper == OP_GT ||
	       oper == OP_LEQ || oper == OP_GEQ;
}

static struct ref compile_expr(struct ir *ir, struct symtab *symtab, struct node *node);

static void compile_boolexpr(
		struct ir *ir, struct symtab *symtab, struct node *node, const char *truedest, const char *falsedest) {

	if (node->type == N_BINOP && oper_is_comparison(node->oper)) {
		struct ref r1 = compile_expr(ir, symtab, node->child1);
		struct ref r2 = compile_expr(ir, symtab, node->child2);
		ir_append(ir, irins_make_12(INS_CMP, r1, r2));
		enum condcode condcode;
		switch (node->oper) {
			case OP_EQ: condcode = CCNZ; break;
			case OP_NEQ: condcode = CCZ; break;
			case OP_LT: condcode = CCGE; break;
			case OP_GT: condcode = CCLE; break;
			case OP_LEQ: condcode = CCG; break;
			case OP_GEQ: condcode = CCL; break;
			default: assert(false);
		}
		ir_append(ir, irins_make_jcc(falsedest, condcode));
		ir_append(ir, irins_make_name(INS_JMP, truedest));
	} else if (node->type == N_BINOP && node->oper == OP_AND) {
		const char *try2lbl = gen_label_name();
		compile_boolexpr(ir, symtab, node->child1, try2lbl, falsedest);
		ir_append(ir, irins_make_name(INS_LBL, try2lbl));
		compile_boolexpr(ir, symtab, node->child2, truedest, falsedest);
	} else if (node->type == N_BINOP && node->oper == OP_OR) {
		const char *try2lbl = gen_label_name();
		compile_boolexpr(ir, symtab, node->child1, truedest, try2lbl);
		ir_append(ir, irins_make_name(INS_LBL, try2lbl));
		compile_boolexpr(ir, symtab, node->child2, truedest, falsedest);
	} else if (node->type == N_UNOP && node->oper == OP_NOT) {
		compile_boolexpr(ir, symtab, node->child1, falsedest, truedest);
	} else {
		struct ref ref = compile_expr(ir, symtab, node);
		ir_append(ir, irins_make_12(INS_TEST, ref, ref));
		ir_append(ir, irins_make_jcc(falsedest, CCZ));
		ir_append(ir, irins_make_name(INS_JMP, truedest));
	}
}

static struct ref compile_expr(struct ir *ir, struct symtab *symtab, struct node *node) {
	switch (node->type) {
		case N_NUM: {
			struct ref ref = ref_next_register();
			ir_append(ir, irins_make_01(INS_MOV, ref, ref_imm(node->value)));
			return ref;
		}

		case N_VAR: {
			struct symbol *sym = symtab_find(symtab, node->name);
			if (!sym) {
				fprintf(stderr, "Use of undeclared variable '%s'\n", node->name);
				exit(1);
			}
			if (sym->stype != ST_VAR) {
				fprintf(stderr, "Cannot use function name in expression\n");
				exit(1);
			}
			return sym->ref;
		}

		case N_BINOP: {
			if (oper_is_basic_arith(node->oper)) {
				struct ref r0 = ref_next_register();
				struct ref r1 = compile_expr(ir, symtab, node->child1);
				struct ref r2 = compile_expr(ir, symtab, node->child2);
				enum instype instype;
				switch (node->oper) {
					case OP_ADD: instype = INS_ADD; break;
					case OP_SUB: instype = INS_SUB; break;
					case OP_MUL: instype = INS_MUL; break;
					case OP_DIV: instype = INS_DIV; break;
					case OP_MOD: instype = INS_MOD; break;
					default: assert(false);
				}
				ir_append(ir, irins_make_012(instype, r0, r1, r2));
				return r0;
			} else if (oper_is_comparison(node->oper) || node->oper == OP_AND || node->oper == OP_OR) {
				const char *truelbl = gen_label_name();
				const char *falselbl = gen_label_name();
				const char *afterlbl = gen_label_name();
				compile_boolexpr(ir, symtab, node, truelbl, falselbl);
				struct ref cval = ref_next_register();
				ir_append(ir, irins_make_name(INS_LBL, truelbl));
				ir_append(ir, irins_make_01(INS_MOV, cval, ref_imm(1)));
				ir_append(ir, irins_make_name(INS_JMP, afterlbl));
				ir_append(ir, irins_make_name(INS_LBL, falselbl));
				ir_append(ir, irins_make_01(INS_MOV, cval, ref_imm(0)));
				ir_append(ir, irins_make_name(INS_LBL, afterlbl));
				return cval;
			} else if (node->oper == OP_ASSIGN) {
				if (node->child1->type == N_VAR ||
						(node->child1->type == N_UNOP && node->child1->oper == OP_DEREF)) {
					struct ref r0 = compile_expr(ir, symtab, node->child1);
					struct ref r1 = compile_expr(ir, symtab, node->child2);
					ir_append(ir, irins_make_01(INS_MOV, r0, r1));
					return r0;
				} else {
					fprintf(stderr, "Invalid left-hand side in assignment.\n");
					exit(1);
				}
			} else {
				assert(false);
			}
		}

		case N_UNOP: {
			switch (node->oper) {
				case OP_NEG: {
					struct ref r0 = ref_next_register();
					struct ref r1 = compile_expr(ir, symtab, node->child1);
					ir_append(ir, irins_make_01(INS_NEG, r0, r1));
					return r0;
				}

				case OP_NOT: {
					struct ref r0 = ref_next_register();
					struct ref r1 = compile_expr(ir, symtab, node->child1);
					const char *afterlbl = gen_label_name();
					ir_append(ir, irins_make_12(INS_TEST, r1, r1));
					ir_append(ir, irins_make_01(INS_MOV, r0, ref_imm(0)));
					ir_append(ir, irins_make_jcc(afterlbl, CCNZ));
					ir_append(ir, irins_make_01(INS_MOV, r0, ref_imm(1)));
					ir_append(ir, irins_make_name(INS_LBL, afterlbl));
					return r0;
				}

				case OP_DEREF: {
					struct ref addr = compile_expr(ir, symtab, node->child1);
					struct ref r1;
					switch (addr.type) {
						case REF_REG: r1 = ref_mem(addr.reg, 0, REFREL_ZERO); break;
						case REF_IMM: r1 = ref_mem(REG_UNUSED, addr.imm, REFREL_ZERO); break;
						case REF_MEM: {
							r1 = ref_next_register();
							ir_append(ir, irins_make_01(INS_MOV, r1, addr));
							r1 = ref_mem(r1.reg, 0, REFREL_ZERO); break;
							break;
						}
					}
					struct ref r0 = ref_next_register();
					ir_append(ir, irins_make_01(INS_MOV, r0, r1));
					return r0;
				}

				case OP_ADDROF:
					fprintf(stderr, "OP_ADDROF not implemented\n");
					exit(1);

				default:
					assert(false);
			}
		}

		case N_CALL: {
			struct symbol *sym = symtab_find(symtab, node->name);
			if (!sym) {
				fprintf(stderr, "Call of undeclared function '%s'\n", node->name);
				exit(1);
			}
			if (sym->stype != ST_FUNC) {
				fprintf(stderr, "Cannot call variable\n");
				exit(1);
			}
			if (node_list_length(node->child1) != sym->numparams) {
				fprintf(stderr, "Invalid number of parameters to function '%s' (typechecker, come on)\n", node->name);
				exit(1);
			}
			struct node **args = malloc(sym->numparams * sizeof(struct node*));
			write_node_list(args, node->child1);
			for (int i = sym->numparams - 1; i >= 0; i--) {
				struct ref r = compile_expr(ir, symtab, args[i]);
				ir_append(ir, irins_make_1(INS_PUSH, r));
			}
			free(args);
			struct ref retref;
			if (node->rtype == type_void()) {
				ir_append(ir, irins_make_name(INS_CALL, node->name));
				retref = ref_reg(REG_UNUSED);  // TODO make nicer; typechecker should've caught usages though
			} else {
				retref = ref_next_register();
				struct irins *ins = irins_make_0(INS_CALLV, retref);
				ins->name = ir_str(node->name);
				ir_append(ir, ins);
			}
			ir_append(ir, irins_make_012(INS_ADD, ref_reg(REG_SP), ref_reg(REG_SP), ref_imm(sym->numparams)));
			return retref;
		}

		default:
			fprintf(stderr, "Invalid node type %d in expression\n", node->type);
			exit(1);
	}
}

static void compile_node(struct ir *ir, struct symtab *symtab, struct node *node) {
	switch (node->type) {
		case N_LIST:
			compile_node(ir, symtab, node->child1);
			compile_node(ir, symtab, node->child2);
			break;

		case N_LIST_END:
			break;

		case N_BLOCK: {
			symtab = symtab_sub(symtab);
			compile_node(ir, symtab, node->child1);
			symtab = symtab_delete_get_parent(symtab);
			break;
		}

		case N_VAR_DECL_INIT:
		case N_VAR_DECL: {
			if (symtab_find_local(symtab, node->name)) {
				fprintf(stderr, "Redeclaration of variable '%s'\n", node->name);
				exit(1);
			}
			struct ref vref;
			if (node->type == N_VAR_DECL_INIT) vref = compile_expr(ir, symtab, node->child1);
			else vref = ref_imm(0);
			struct symbol *sym = symbol_make_var(strdup(node->name), node->rtype);
			if (symtab->parent == NULL) sym->ref = ir_reserve_global(ir, 1);
			else sym->ref = ref_next_register();
			symtab_insert(symtab, sym);
			ir_append(ir, irins_make_01(INS_MOV, sym->ref, vref));
			break;
		}

		case N_FUNC_DECL: {
			if (memcmp(node->name, "__", 2) == 0) {
				fprintf(stderr, "Invalid function name '%s' (cannot start with '__')\n", node->name);
				exit(1);
			}
			if (symtab_find(symtab, node->name)) {
				fprintf(stderr, "Redeclaration of function '%s'\n", node->name);
				exit(1);
			}
			int numparams = node_list_length(node->child1);
			struct symbol *sym = symbol_make_func(strdup(node->name), node->rtype, numparams);
			write_func_params(sym->params, node->child1);
			symtab_insert(symtab_root(symtab), sym);

			ir_append(ir, irins_make_name(INS_LBL, node->name));

			symtab = symtab_sub(symtab);
			for (int i = 0; i < numparams; i++) {
				struct symbol *parsym = symbol_make_var(strdup(sym->params[i].name), sym->params[i].type);
				parsym->ref = ref_mem(REG_BP, 2 + i, REFREL_ZERO);
				symtab_insert(symtab, parsym);
			}

			compile_node(ir, symtab, node->child2);

			symtab = symtab_delete_get_parent(symtab);

			// necessary for void functions, to be sure otherwise
			ir_append(ir, irins_make(INS_RET));
			break;
		}

		case N_IF: {
			const char *thenlbl = gen_label_name();
			const char *elselbl = gen_label_name();
			const char *afterlbl = gen_label_name();
			compile_boolexpr(ir, symtab, node->child1, thenlbl, elselbl);
			ir_append(ir, irins_make_name(INS_LBL, thenlbl));
			compile_node(ir, symtab, node->child2);
			ir_append(ir, irins_make_name(INS_JMP, afterlbl));
			ir_append(ir, irins_make_name(INS_LBL, elselbl));
			compile_node(ir, symtab, node->child3);
			ir_append(ir, irins_make_name(INS_LBL, afterlbl));
			break;
		}

		case N_WHILE: {
			const char *startlbl = gen_label_name();
			const char *bodylbl = gen_label_name();
			const char *afterlbl = gen_label_name();
			ir_append(ir, irins_make_name(INS_LBL, startlbl));
			compile_boolexpr(ir, symtab, node->child1, bodylbl, afterlbl);
			ir_append(ir, irins_make_name(INS_LBL, bodylbl));
			compile_node(ir, symtab, node->child2);
			ir_append(ir, irins_make_name(INS_JMP, startlbl));
			ir_append(ir, irins_make_name(INS_LBL, afterlbl));
			break;
		}

		case N_RETURN:
			ir_append(ir, irins_make(INS_RET));
			break;

		case N_RETURNV: {
			struct ref ref = compile_expr(ir, symtab, node->child1);
			ir_append(ir, irins_make_1(INS_RETV, ref));
			break;
		}

		default:  // hmm, maybe it's an expression statement?
			compile_expr(ir, symtab, node);
			break;
	}
}

static void compile_data_setup_node(struct ir *ir, struct symtab *symtab, struct node *node) {
	switch (node->type) {
		case N_LIST:
			if (node->child1->type == N_VAR_DECL || node->child1->type == N_VAR_DECL_INIT) {
				compile_node(ir, symtab, node->child1);
				node_delete_recursive(node->child1);
				node->child1 = node_make_0(N_LIST_END);
			}
			compile_data_setup_node(ir, symtab, node->child2);
			break;

		case N_LIST_END:
			break;

		case N_VAR_DECL:
		case N_VAR_DECL_INIT:
			compile_node(ir, symtab, node);
			break;

		case N_FUNC_DECL:
			break;

		default:
			assert(false);
	}
}

static void compile_data_setup(struct ir *ir, struct symtab *symtab, struct node *root) {
	struct ref flag = ir_reserve_global(ir, 1);
	ir_append(ir, irins_make_12(INS_TEST, flag, flag));
	const char *afterlbl = gen_label_name();
	ir_append(ir, irins_make_jcc(afterlbl, CCNZ));

	compile_data_setup_node(ir, symtab, root);
	ir_append(ir, irins_make_01(INS_MOV, flag, ref_imm(1)));

	ir_append(ir, irins_make_name(INS_LBL, afterlbl));
	ir_append(ir, irins_make_name(INS_CALL, "main"));
	ir_append(ir, irins_make(INS_BRK));
}

struct ir* compile(struct node *node) {
	struct ir *ir = ir_make();
	struct symtab *symtab = symtab_make();
	compile_data_setup(ir, symtab, node);
	compile_node(ir, symtab, node);
	return ir;
}